75 280z 2+2

Hello to all, forgive me I'm new at this. What I have is a 75 280z 2+2 and I want to put a V8 into it. This is a father son project that we have been working on for a while now and we are close to the point where the decision of what type of V8 is the best. I would like a lot of torque but something that is affordable. What kits are the best for a change over, engine and transmission, would like to keep the car a automatic. I have heard 96 newer 3.5 fuel injected truck engine and tranny would be a good and reliable set-up. Any suggestions? thanks